Determination of aerodynamic forces and moments on an aircraft is critical to aircraft design and safe operation during weather-based disturbances. Aerodynamic loads and moments predicted by theoretical models, however, generally differ from the loads and moments experienced under actual flight conditions, largely due to the dominating role of viscous effects and their interactions with the structure.
As described in U.S. Pat. No. 6,826,493 (493 patent) and U.S. Pat. No. 6,963,810 (810 patent), the complete disclosures of which are incorporated herein by reference in their entirety, methods have been developed to relate aerodynamic loads and moments to flow data that can be measured without regard to structural response. These methods involve correlating aerodynamic loads and moments to the spatial locations of critical flow feature indicators (CFFIs), which are associated with certain flow phenomena such as flow bifurcation points, shock waves, and the transition from laminar to turbulent flow. As used herein, the term “flow bifurcation point” (FBP) means a location on a body surface where the flow attaches to or separates from the body. As illustrated in FIG. 1, the FBPs associated with an airfoil 10 may include leading edge stagnation point (LESP) 20, flow separation point (FSP) 30, and flow reattachment point (FRP) 40. The '493 and '810 patents also described how the CFFIs associated with these phenomena can be determined from shear stress and convective heat transfer data obtained from hot film sensors formed on or adhered to the surface of a body immersed in steady or unsteady flow regimes.
In U.S. Pat. No. 8,306,800 (800 patent) the complete disclosure of which is incorporated herein by reference in its entirety, methods are disclosed for modeling aerodynamic forces and moments using FBPs and other CFFIs. In particular, the '800 patent discloses a mathematical model based on potential flow theory combined with conformal transformation. Among other approaches, the model allows the computation of aerodynamic coefficients based on the specification of two FBPs (e.g., LESP and FSP) for a given flow regime.
The above-cited references describe methods for measuring flow parameters and computing aerodynamic coefficients and loads in real time for immersed bodies. The '800 patent, in particular, focused on measurement of flow parameters near the leading edge using hot-film sensors. Embodiments of the present invention extend these methods to provide robust and efficient methods of providing aerodynamic and hydrodynamic load information based on relatively limited sensor data at a distance downstream of the leading-edge.
It will be understood by those of ordinary skill in the art that the methods of the present invention apply to all fluid flow regimes. Thus, although the term “aerodynamic” is used throughout in describing the embodiments of the invention, the invention may also be used in hydrodynamic applications or applications involving any other fluid flow regime.